Method for operating a pump

ABSTRACT

A method for operating a switchable pump, which is situated in a motor vehicle and configured to provide a setpoint pressure for a medium, the pump being activated in trailing-throttle operation of the motor vehicle.

RELATED APPLICATION INFORMATION

The present application claims priority to and the benefit of German patent application no. 10 2011 085 759.1, which was filed in Germany on Nov. 4, 2011, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method for operating a pump, and to a control unit.

BACKGROUND INFORMATION

In unthrottled engines such as Diesel engines or gasoline engines, in which a jet-directed combustion method or high-pressure supercharging is employed, a vacuum pump is used to provide sufficient negative pressure. This negative pressure typically is used for a brake booster or to control another component assembly, e.g., for a bypass valve or boost-control valve of a turbocharger. The vacuum pump normally is driven continuously, via the camshaft. Since driving the vacuum pump consumes additional fuel, the use of switchable vacuum pumps is increasing. In such a case the vacuum pump is connected only if a drop occurs in the negative pressure in the brake booster, for instance because the brake has been operated. This need-based control lowers the losses caused by the vacuum pump.

SUMMARY OF THE INVENTION

Against this background, a method and a control unit are provided which have the features described herein. Additional developments of the exemplary embodiments and/or exemplary methods of the present invention result from the description herein.

In one development, the exemplary embodiments and/or exemplary methods of the present invention provide for realizing the control of a switchable pump in a motor vehicle, e.g., a switchable vacuum pump, the switchable pump predominantly being activated automatically in trailing-throttle operation with a switched-off engine, and switched on and/or activated in this manner. If the motor vehicle is operated under a load when the engine of the motor vehicle is on, the pump need not be activated.

If the motor vehicle is operated under a load, its wheels are driven by the running engine when the clutch is closed. In such a case an engine implemented as internal combustion engine is combusting fuel. In trailing throttle operation, it is provided that the engine is switched off and driven via the running wheels and/or via the moving vehicle, and thus is pushed and/or towed while the clutch is closed. In trailing throttle operation, no fuel is combusted by an engine implemented as internal combustion engine.

With the aid of the exemplary embodiments and/or exemplary methods of the present invention the losses of the switchable pump are able to be reduced, among other things. The switchable pump, in most cases a vacuum pump, is actuated, and thus controlled and/or regulated, by a control unit of an engine management, for instance. In the process the control unit may switch the pump as a function of an operating state of the motor vehicle, the pump being switched on automatically by the control unit when the motor vehicle is in trailing throttle operation and/or as soon as the motor vehicle transitions to trailing throttle operation. As a rule, the control unit switches the pump off again, or even refrains from switching it on in the first place, when the motor vehicle is operating under a load.

The control unit is able to check whether the motor vehicle is in trailing throttle operation or in load operation, by monitoring a function of other components of the motor vehicle, e.g., the engine, the transmission and/or the wheels. In addition, the control unit is able to ascertain whether the motor vehicle changes from load operation to trailing throttle operation or from trailing throttle operation to load operation, and thus changes its operating state.

If the control unit in the engine management detects that the motor vehicle is in trailing throttle operation, then the pump, implemented as vacuum pump, for instance, is automatically activated, such as switched on. The power used to drive the pump may be obtained by utilizing the brake energy and/or the inertia weight of the motor vehicle. As a result, no additional fuel is consumed to drive the pump since the engine of the motor vehicle is switched off in trailing throttle operation and the motor vehicle is decelerated as a rule.

Using the pump, a pressure therefore is able to be provided, usually built up or dissipated, in a pressure reservoir of a medium, until the pressure of the medium has reached a predefined setpoint pressure. Oil or some other fluid, for example, may be used as medium. If the pump is developed as vacuum pump, the pressure reservoir is recharged with negative pressure as setpoint pressure during trailing throttle operation.

The pressure reservoir furthermore is able to cooperate with a brake booster. In one development of the method, the medium for operating the brake booster may feature the predefined setpoint pressure, such as vacuum pressure. As a result, a brake system of the motor vehicle is able to be actuated multiple times. In general, trailing throttle operation arises before the brake system is actuated, so that sufficient setpoint pressure, normally sufficient vacuum pressure, is made available during trailing throttle operation. This prevents the vacuum pump from using drive torque of the engine when the engine is switched on; in other words, the vacuum pump is able to be switched off when the engine is on.

However, if the pressure deviates significantly from the setpoint pressure in the brake booster during load operation nevertheless, it is possible to connect the vacuum pump also during load operation when the engine is on, but this will lead to higher fuel consumption.

The pump is able to be deactivated in trailing-throttle operation as well after a settable time and/or after a set time interval has elapsed, provided it is ensured that the pressure reservoir of the brake booster is fully charged following this time interval. As a rule, the pump is able to be switched off when the medium has reached the setpoint pressure to be attained, e.g., vacuum pressure. At least one further pressure reservoir may be provided in addition, which then is likewise charged by the pump in trailing throttle operation while providing the setpoint pressure. Using the at least one additional pressure reservoir, additional consumers, e.g., additional vacuum pressure consumers, are able to be supplied.

The control unit according to the exemplary embodiments and/or exemplary methods of the present invention is configured to execute all of the steps of the method provided. Furthermore, functions of the control unit are implementable as steps of the method. In addition, it is possible to realize the steps of the method as functions of the control unit.

Further advantages and embodiments of the present invention are derived from the description and the accompanying drawing.

It is understood that the features mentioned above and the features yet to be described may be used not only in the individually given combination but also in other combinations or in isolation, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 schematically shows a system which includes a specific development of a control unit according to the present invention.

DETAILED DESCRIPTION

System 1 schematically shown in FIG. 1 is situated in a motor vehicle (not shown further). This system 1 includes a specific development of a control unit 3 according to the present invention, and a switchable pump 5 which is developed as vacuum pump in this instance. In addition, system 1 includes an engine 7 of the motor vehicle implemented as combustion engine, and a camshaft 9 which is assigned to engine 7. If pump 5 is switched on, it is provided that pump 5 is coupled to engine 7 via camshaft 9, and thus is driven by engine 7 via camshaft 9.

Moreover, switchable pump 5 is connected to a pressure reservoir 11 for a medium. It is provided that pump 5 cooperates with pressure reservoir 11. If pump 5 is switched on and thus driven by engine 7, it is possible that operating pump 5 generates a setpoint pressure for the medium inside pressure reservoir 11.

If pump 5 is implemented as vacuum pump, as in the case at hand, a vacuum pressure is generated in pressure reservoir 11. In the specific development described, pressure reservoir 11 cooperates with a component assembly 13 of the motor vehicle, which normally is able to be operated when the medium inside pressure reservoir 11 features the setpoint pressure as a minimum.

In one embodiment of the present invention, it may be provided that component assembly 13 is developed as a component of a brake system for the motor vehicle, such as as a brake booster of the brake system. In this case component assembly 13 developed as brake booster generally is able to be operated when a vacuum pressure as the setpoint pressure is present inside pressure reservoir 11.

Control unit 3 is developed to control an operation of switchable pump 5 which is situated inside the motor vehicle and developed to provide the setpoint pressure for the medium. Control unit 3 activates or switches on pump 5 when the motor vehicle is in a trailing-throttle state.

Pump 5 is activated automatically in the process and thus switched on when the motor vehicle is in a trailing-throttle state and/or when the motor vehicle transitions to a trailing-throttle state. In other words, pump 5 is used to set the setpoint pressure for the medium inside pressure reservoir 11. If pump 5 is developed as vacuum pump, a vacuum pressure is generated as setpoint pressure for the medium, which vacuum pressure is used to operate a brake booster as component assembly 13 of the motor vehicle.

However, if insufficient setpoint pressure is present, it is also possible that pump 5 is driven by engine 7 of the motor vehicle even in the switched-on state. As a rule, the already activated pump 5 is deactived in the trailing-throttle state and thus switched off if the pressure of the medium has reached the setpoint pressure. 

What is claimed is:
 1. A method for operating a switchable pump, which is situated in a motor vehicle and configured to provide a setpoint pressure for a medium, the method comprising: activating the pump during a trailing-throttle operation of the motor vehicle.
 2. The method of claim 1, wherein the pump is activated automatically when the motor vehicle transitions to trailing-throttle operation.
 3. The method of claim 1, wherein the pump is used to set the setpoint pressure in a pressure reservoir for the medium.
 4. The method of claim 1, wherein the pump includes a vacuum pump, and wherein a vacuum pressure is generated as setpoint pressure for the medium with the vacuum pump.
 5. The method of claim 1, wherein the setpoint pressure generated by the pump is used to operate a brake booster.
 6. The method of claim 1, wherein the pump is driven by an engine of the motor vehicle in the switched-on state.
 7. The method of claim 1, further comprising: switching off the pump in a trailing-throttle operation when the pressure of the medium has reached the setpoint pressure.
 8. A control unit for controlling an operation of a switchable pump, which is situated in a motor vehicle and configured to provide a setpoint pressure for a medium, comprising: a control arrangement configured to activate the pump in a trailing-throttle operation of the motor vehicle. 